Date of Graduation


Document Type

Problem/Project Report

Degree Type



Statler College of Engineering and Mineral Resources


Lane Department of Computer Science and Electrical Engineering

Committee Chair

Roy S. Nutter Jr.

Committee Member

Brian Woerner

Committee Member

Mohamed Hefeida


Extremely low frequencies signals are waves between 3 to 30Hz and corresponding wavelengths between 10,000 to 100,000 kilometers. The specific signals used here are generated from lightning and are excited at frequencies around 8Hz, 14Hz, 20Hz. These are often called Schumann Resonance frequencies. Several stations have been built around the world for identifying ELF waves. All of those required a sparsely populated area that was far away from electric power lines because of interference from electric noise at 50 Hz and 60Hz. This project develops and tests an amplifier and filter circuit that should assist in identifying the Schumann Resonance signals in more electrically noisy environments. Detecting these extremely small signals requires circuits which have low internal noise among other characteristics. Analog Devices has recently produced a Precision Signal Conditioning Integrated Circuit (the AD8421) which has very low internal noise. The work reported herein uses Analog Devices' new chip and amplifies these very low voltages and then actively filters electric noise at these low frequencies using the AD8510. A Printed Circuit Board (PCB) was designed to help shield the circuit from the interference of higher frequencies in the surrounding environment. This design detects input voltages below 5 micro volts and gives a significantly amplified output. Voltage vs frequency and input vs output voltage characteristics are plotted for this design.